It is well known that oil and gas well exploration involves the generation of waste water products, including fluid wastes in the nature of either drilling fluids or fracture or return fluids from the drilling operation. Typically, drilling pits are excavated by a well operator, near the drilling site, to receive these fluid waste products. Environmental clean-up requirements, imposed by the EPA and local government agencies, require the responsible party associated with the drilling operations to remediate the drilling site and, in particular, any drilling pits and related fluid waste products.
Depending upon applicable environmental requirements, responsible parties associated with drilling operations have had limited options in respect to clean up of drilling pits and related fluid waste products. In certain states, it is possible to pump the waste fluids into an injection well, e.g., an exhausted oil or gas well, after the fluid waste is filtered and, possibly, chemically treated. In states with more stringent environmental requirements, such as Pennsylvania, the responsible party associated with the drilling operations typically is forced to incur the expense of transporting the fluid waste products in the drilling pits to a properly licensed disposal site and/or reclamation operation.
In the context of offsite drilling waste fluids treatment, the prior art discloses various processes for chemical treatment or filtration of the contaminants within this fluid waste. For example, U.S. Pat. No. 4,465,598 teaches the precipitation of metals including iron, nickel, chromium, cobalt, and manganese in oil and gas well heavy brines which have been filtered initially to remove solids. U.S. Pat. No. 4,634,533 teaches an oil and gas well brine treatment including an initial oxidizing treatment to convert iron to the ferric state. U.S. Pat. No. 5,814,230 describes an apparatus and method for separation of solids from liquid for use with different processes. In particular, this invention describes the separation of solids from a liquid flow using an endless conveyor carrying screen filters which dredge gravity-settled solids from the bottom of a settling tank and filter solids suspended in the flowing liquid. The solids are further dewatered while on the filters using a combination of vibration and air streams. U.S. Pat. No. 4,436,635 describes a filtering process for filtration of oil and gas well treatment fluids.
Offsite treatment of drilling waste fluids is uneconomical, however, because of the transportation costs associated in transporting the fluid waste to a reclamation or treatment area. As such, it has become desirable for responsible parties involved in well drilling operations to attempt to reuse fluid waste. In particular, absent permitted reuse of the drilling fluid waste products, the drilling operator is required to use new, fresh water for ongoing drilling operations. In the absence of a ready source for such fresh water, or in drought conditions, the drilling operator is required to bring water on-site for the continuing drilling operations, which again involves a high trucking cost for the movement of water. Thus, a need exists to develop an economical method for on-site treatment of drilling fluid wastes which would allow these fluid wastes, after treatment, to be reused in drilling operations.
The prior art reveals several efforts to address this need, however, these efforts continue to involve high economic costs and/or do not satisfy strict environmental requirements that exist for fluid reuse in certain states. For example, U.S. Pat. No. 4,895,665 teaches a method for treating and reclaiming oil and gas well working fluids and the related drilling pits. In particular, this patent teaches a method of chemical treatment and filtration of oil and gas well working fluids within the associated drilling pits. In contrast to the present invention, however, the primary purpose of this patent is to prepare a drilling pit for closure through reduction of the fluid content in sludge which is formed in the drilling pit. While the water treated through the teachings of the '665 patent can be reused, the process taught by the '665 patent is much more expensive and time consuming than the present invention.
U.S. Pat. No. 5,093,008 (the “'008 patent”) teaches a process and apparatus for recovering reusable water from waste drilling fluid. More specifically, this invention teaches a dewatering process and apparatus for concurrent reutilization of water in waste drilling fluids from an active drilling operation that includes a storage area, an intermixer for introducing treatment chemicals into the waste drilling fluids and a centrifuge. Flocculation is chemically induced in the waste drilling fluids as they pass through the intermixing needs for introducing treatment chemicals into the waste drilling fluids. The waste drilling fluids are then transferred to a centrifuge where solid waste is separated from clear, reusable water. The water is returned to the storage area and may be chemically adjusted prior to being returned to the drilling rig. Unlike the present invention, however, the '008 patent does not involve treatment of waste fluid water in the drilling pit, and the '008 patent involves a process which is much more complicated and expensive than the present invention.
U.S. Pat. No. 4,536,286 (the “'286 patent”) describes a self-contained, portable waste treatment system for hazardous and non-hazardous waste comprising a pair of mixing tanks. Solids are removed from fluid waste streams by flocculation and related solids deposition. The primary purpose of the '286 patent is waste water clean-up in connection with a variety of processes including chemical manufacturing, food processing, mining and the exploration and drilling of oil and gas wells. The '286 patent does not contemplate reuse of drilling fluid waste after treatment. Also, unlike the present invention, the '286 patent does not provide for a filtration step. Further, the present invention allows for treatment of a greater volume of waste water in less time.
Finally, U.S. Pat. No. 5,520,803 (the “'803 patent”) describes a mobile waste water treatment device. The '803 patent is described as having particular application for the treatment of heavy metals, paint residues, fats, oils, and grease and is not described as having application to waste fluids resulting from oil and gas well drilling operations.
In contrast to this prior art, the present invention provides a mobile waste water treatment system designed for specific use in the drilling pits associated with oil and gas well drilling operations. As described more fully below, the present invention provides an economical means of treating drilling waste fluids so that they can be either reused at the same site or transported to a new drilling operation.